Continuous action board press

ABSTRACT

The present invention concerns a continuous action board press in which the board material to be pressed is first subjected to pressure by a press roll and thereafter comes into a pressure chamber, in which a medium under pressure imposes a load upon the board material. According to the invention the pressure chamber extends up to the said press roll so that the press roll constitutes the front wall of the pressure chamber and that the surfaces defining the pressure chamber have been sealed against the press roll. A board press is here understood to be a press which may be employed for pressing boards, such as plywood, chip, fiber and other boards, for laminating various kinds of boards, for providing any kinds of boards with a surfacing layer, etc. In all these instances the boards have to be subjected to pressure. The boards may be in the form of a long web or in the form of shorter pieces, which are consecutively fed into the press. In order that the handling of the boards to be manufactured or processed might take place in a flexible manner, endeavors have been made to introduce, instead of presses operating according to the individual charge principle, continuous action presses. One such continuous action press, in which press belts and a pressure medium are used, has the drawback that the press roll and the initial end of the pressure chamber are spaced with reference to each other by a given distance. The board material to be pressed, which has been compressed by the press roll to its ultimate thickness or to a fraction thereof, tends as a result of its elasticity to return to its original thickness before it enters the pressure chamber. As a result, the board material compels the press belt to make a bend between the press roll and the initial end of the pressure chamber. The point of steepest bending is located at the front wall of the pressure chamber. This bend, or wave, has the effect that the press belt is rapidly worn out and has to be replaced.

United States Patent Kerttula et al. 1 Sept. 5, 1972 [54] CONTINUOUS ACTION BOARD PRESS board material. According to the invention the pres- [72 Inventors; m Isak g m Luotsikatu 18 3, sure chamber extends up to the said press roll so that Hetsinki p Amo Janine, the press roll constitutes the frontwall of the pressure Koivikkotie 2 Helsinki both f chamber and that the surfaces defining the pressure Finland chamber have been sealed against the press roll. [22] Fil d; A il 23, 1971 A board press is here understood to be a press which may be employed for pressing boards, such as [21] Appl' 138,258 plywood, chip, fiber and other boards, for' laminating g various kinds of boards, for providing any kinds of [30 p A fi p i -i Data boards With a surfacing layer, etc. In all these in- 1 p ty stances the boards have to be subjected to pressure. 30, "1232 The may in the fon'n of a long web or in the form of'shorter pieces, which are consecutively fed [52 US. Cl. "100/154, 100/93 P, 115566759872, into the press I 51] rm. c1. 83% 5/04 Order that the handling Ofthe boards t be m y 58 Field of Search ..1oo/151,152,153,1s4,15s, factufed 0r Processed ""8 take P e a 'P 100/160, 144, 93, 211, 295; 156/497, 555, manner, endeavors have been made to introduce, in-

425/107 stead of presses operating according to the individual charge principle, continuous action presses. One such 5 References Cited continuous action press, in which press belts and a pressure medium are used, has the drawback that the UNITED STATES PATENTS press roll and the initial end of the pressure chamber are spaced with reference to each other by a given 3:23: distance. The board material to be pressed, which has 3'340795 9/1967 Hartley:II IIII II 100/154 been mpressed by P'ess Primary Examiner-Peter Feldman Attorney-Waters, Roditi, Schwartz & Nissen 57] ABSTRACT thickness or to a fraction thereof, tends as a result of its elasticity to return to its original thickness before it enters the pressure chamber. As a result, the board material compels the press belt to make a bend between the press roll and the initial end of the pressure chamber. The point of steepest bending is located at the front wall of the pressure chamber. This bend,

' or wave, has the effect that the press belt is rapidly worn out and has to be replaced.

A Claims, 5 Figures PATENTEBsEP 5 I 12 SHEU 1 0F 2 vvvvvv I 1 CONTINUOUS ACTION BOARD PRESS The aim of the present invention is to accomplish a continuous action board press which is free of the drawbacks mentioned above. The invention is mainly characterized in that the press roll constitutes the front wall of the pressure chamber and that the surfaces confining the pressure chamber have been sealed against the press roll.

In a board press according to the invention the pressure acting upon the belt and thus also upon the board material to be pressed begins as a pressure produced by the press roll and continues immediately as a pressure generated by the pressure chamber. Thus no bend is produced in the press belt, for which reason the service life of the press belt increases. In aboard press according to the invention the pressure produced by the press roll has to be comparatively high in order that the pressure prevailing in the pressure chamber might not be able to discharge through the gap between the press roll and the press belt. The pressure produced by the press roll is most appropriately equal to or some what higher than the pressure generated by the pressure chamber.

But with the aid of a press according to the invention one achieves as an unexpected additional advantage that a press belt or press belts are not needed at all, especially if the board material to be pressed possesses sufficient rigidity and coherence already before the pressing process. It should be noted that one of the tasks of the belt is to guide the board material to be pressed into the pressure chamber. In a press according to the invention this guidance is furnished by the press roll.

The invention is described with the aid of an example in the following,'with reference to the attached drawing, wherein FIG. 1 shows a board press according to one embodiment, in longitudinal section,

FIG. 2 shows the section along line II-II in FIG. 1,

FIG. 3 corresponds to FIG. 2 and shows another embodiment,

FIG. 4 corresponds to FIG. 1 and shows another embodiment, and

FIG. 5 shows the section along line V-V in FIG. 4.

In FIGS. 1 and 2, the press consists of two endless belts l, which between them define the press gap. The belts, which may consist e.g., of steel, pass over press rolls 2 and 3. The rolls on the right in FIG. 1, 3, are rolls providing traction. The board material to be pressed consists in the case depicted in the figure, of veneers 4, which are fed into the press gap between the belts 1, whence they emerge as a finished, pressed sheet of plywood, 5.

Pressing takes place at first by means of the press rolls 2, which compress the board material 4 to its final thickness. Immediately thereafter the press belts 1 and the board material enclosed between them come under pressure of the medium, such as air, in the pressure chambers 6.

In both pressure chambers 6 the front wall is formed by the press roll 2. The roof 7 of the pressure chamber has been scaled against the press roll 2 by a seal 8 parallel to the lateral line of the roll. The front ends of the side walls 9 of pressure chamber 6 have been sealed against the end faces of roll 2 by seals 10. The lower edges of the side walls of pressure chamber 6 have been sealed against the belts 1 by seals 14. As can be seen from FIG. 1, action of the pressure medium begins already at the vertical centerline of the press roll 2.

According to FIG. 2, the pressure chamber 6 terminates in an end wall 11. The plywood 5 has already become stabilized at this stage to such extent that there is no longer any risk that the press belt 1 would form a bulge at the point between the end wall 11 and the roll 3. But if such risk is present, the possibility exists to design the ultimate end of the pressure chamber 6 to be similar to its initial end.

The embodiment according to FIG. 3 differs from the foregoing in that the side walls of the pressure chamber have been sealed by seals 12 entering grooves 13 in the roll 2, which are parallel to the circumferenc of the roll and are located close to its ends.

It is obvious to one skilled in the art that various embodiments of the invention may vary within the scope of the patent claims set forth below. For instance, the moving surfaces defining the press gap need not be mutually identical. Below the press gap, for instance, a pressure chamber is not indispensable because the lower side merely constitutes a backing for the pressure produced by the top-side pressure chamber 6. This backing may consist of a moving surface formed in any one of a plurality of difierent ways.

On the other hand the press may be designed to be such that one and the same pressure chamber extends both over and under the press gap. Such an instance has been presented in FIGS. 4 and 5. The board materialto be pressed, 4, travels in a press gap defined on top and below by press belts 1 and on the sides by endless sealing belts l5 travelling along with the press belts. Both ends of the pressure chamber have been sealed with a seal having parts 8 parallel to the lateral line of rolls 2 and 3, parts 10 touching the ends of the rolls, parts 16 encircling the endless sealing belts 15, etc. The pressure chamber is thereby sealed in such manner that the pressure medium cannot escape and cannot bleed into the press gap between the belts l.

The pressure medium supplied into the pressure chambers may be at elevated temperature, for which reason the heating of board material to be pressed which may be necessary now and then is accomplished without any other expedients.

The belt or belts 1 may not only consist of steel but e.g., also of rubber. It can be stated in general that the material and design of the belt is chosen in accordance with the properties which one desires the board materialto be pressed to have. It is also possible to choose a modification in which the belts 1 are not endless but instead are lamination strips taken ofl a reel, which after passing through the press gap remain permanently adherent to the board material to be pressed. As has been said before, in a press according to the invention one may in some cases even totally omit the belts.

We claim:

1. Improvement in a continuous action board press in which the board material to be pressed first is subjected to pressure by a press roll and then enters a pressure chamber, in which the board material to be pressed is loaded by a pressure medium, wherein the improvement comprises in that the pressure chamber extends up to the said press roll so that the press roll constitutes the front wall of the pressure chamber and that the surfaces defining the pressure chamber have been scaled against the press roll.

2. Board press according to claim 1, in which the pressure chamberis defined on top by a roof and on the sides by side walls, characterized in that the roof of the pressure chamber has been scaled against the press roll bya seal parallel to the lateral line of the roll and that the side walls of the pressure chamber have been sealed against the end faces of the press roll.

3. Board press according to claim 1, characterized in that the side walls of the pressure chamber have been 7 

1. Improvement in a continuous action board press in which the board material to be pressed first is subjected to pressure by a press roll and then enters a pressure chamber, in which the board material to be pressed is loaded by a pressure medium, wherein the improvement comprises in that the pressure chamber extends up to the said press roll so that the press roll constitutes the front wall of the pressure chamber and that the surfaces defining the pressure chamber have been sealed against the press roll.
 2. Board press according to claim 1, in which the pressure chamber is defined on top by a roof and on the sides by side walls, characterized in that the roof of the pressure chamber has been sealed against the press roll by a seal parallel to the lateral line of the roll and that the side walls of the pressure chamber have been sealed against the end faces of the press roll.
 3. Board press according to claim 1, characterized in that the side walls of the pressure chamber have been sealed in grooves in the roll which run parallel to its circumference and are located close to its ends.
 4. Board press according to claim 1, in which the board material to be pressed passes through the nip of a press roll both at the beginning and at the end of the press gap, characterized in that the pressure chamber extends up to both press rolls and that the surfaces defining the pressure chamber have been sealed against both press rolls. 